Aircraft doors are used in normal operating conditions for passengers boarding and disembarking , they also serve for:
The sizes and distribution of the doors are the result of the facilitation of all these operations for the practical use of the crew, pilots and cabin crew, passengers and the various services involved in carrying out a flight operation before and after the flight.
But more important than the functions mentioned above in normal conditions, the size, the number and the distribution of exits along the fuselage are the result of the application of strict safety rules: indeed, the certification of an aircraft requires that the cabin configuration allows evacuation of passengers and crew members in 90 seconds.
The aircraft manufacturer proceeds, for the purposes of certification, to an exercise / simulation of occupant evacuation using only half of the available exits.
An aircraft manufacturer must therefore, in order to meet this requirement, size and distribute the exits along its fuselage and symmetrically to the right and to the left, considering the case where the density of seats is maximum.
The devices for opening the exits must be simple to operate and their operation must not require excessive effort under the most unfavorable opening conditions.
The corresponding instructions for opening must be visible, easy to recognize and written in the airline country language, and at least another ICAO official language. The use of pictograms can also be used.
Each emergency exit must be fitted with a locking and protection device preventing it from opening in flight either following an untimely maneuver by the occupants, or following a mechanical failure of the normal opening system.
All passenger emergency exits, their means of access and their means of opening are clearly visible and comply with the following requirements:
Certification requirements for civil [commercial] aircraft are derived from ICAO Annex 8 Airworthiness of Aircraft [ICAO, 2016] and the ICAO Airworthiness Manual, Part V State of Design and State of Manufacture [ICAO, 2014]. Each ICAO contracting state then establishes its own legal framework to implement the internationally agreed standards and recommended practices.
You have understood that the most important role of an aircraft exit is that of ensuring the evacuation of passengers when necessary in the best possible conditions.
Therefore, certain considerations are taken into account when an exit is unserviceable.
Let's start first by defining an unserviceable exit.
An exit is considered unserviceable if one of the following exit components is inoperative:
Below is a description of the 5 components:
Interior or exterior opening mechanism
The interior or exterior opening mechanism is the tool that allows the cabin crew member to open the doors from the inside or, if necessary, from the outside. This system differs from one type of aircraft to another.
Let’s take the example of an Airbus 320:
This type of aircraft has four doors quipped with evacuation slides.
From the inside, the flight attendants open the door by lifting the RED door handle upwards to the "Open" position to open the door.
From the outside, the flight attendant introduces his/her hand below the 'PUSH HERE' handle and lifts the handle upwards in the direction of the arrow.
If the door has been forgotten armed, that is to say, connected to the evacuation slide it will be systematically disarmed.
We will come back to this procedure later in a dedicated post.
For the case of the Boeing 737:
The Cabin Crew opens the door by moving the operating handle from the locked position to the open position under both conditions (normal and emergency).
For the opening from the outside, the Cabin Crew pulls the handle and proceeds to a left rotation which will trigger the opening of the door.
Please note that the Boeing 737 does not have the same systematic security for disarming the slide similar to the Airbus 320 , which requires ensuring that the door is properly disarmed before opening it from the outside.
Opening assistance device
Each door has an opening assistance device that allows the flight attendant to use it as a support to help open and close the door.
Door open locking system
To ensure that the door is locked in the open position, the Cabin Crew Member must push the door outwards and guide it with the operating handle to the ‘’ Locked open position''.
The door locks automatically.
Auxiliary evacuation means
Each door has a single-lane or dual-lane slide with automatic inflation.
For the correct functioning of the A320 slide, for example, the door has:
In the case of the A320, the arming of the slide is done by controlling on the Arming lever by putting it in the “Armed” position and disarming by lifting the lever upwards to the “Disarmed” position.
For the B737, arm and disarm manually by inserting or removing a retaining bar on the floor fixing fittings.
For both types, the slide is deployed and inflated as soon as the Cabin Crew opens a door in the Armed position.
Emergency lighting is often a LED lighting, ensuring the recognition and use of evacuation slide and allowing the evacuation of the aircraft.
Now that we have seen the essential components of the door with, if applicable, the designation of a door as unusable in the event of malfunction of at least one of these components, we will now see the actions to be taken by the Cabin Crew if a door is considered inoperative.
When an exit is unserviceable, the Cabin Crew Member must ensure the following:
An Airline cannot use an airplane for passengers transport purposes if:
All aircraft must be equipped with devices to facilitate the evacuation of all passengers in the event of an emergency:
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